1. Field of the Invention
Disclosed herein are polyblend molding compositions which exhibit smoke evolution levels of less than 300 D.sub.m (Flaming) and UL-94 ratings of at least V-1. The polyblends comprise (A) a polymethylmethacrylate (PMMA) matrix polymer; (B) polychloroprene rubber which is grafted with methylmethacrylate (MMA); and (C) a metal oxide.
2. Description of the Prior Art
Polymethylmethacrylate (PMMA) based molding compositions are well known in the art. These materials are also known to burn readily and cleanly, i.e., with little evolution of smoke. When the PMMA is rubber-modified in order to obtain improved impact strength, the material still burns usually with increased amounts of smoke evolution due to the rubber component.
When the rubber-modified PMMA is formulated with flame retardant additives such as antimony oxide and decabromodiphenyl ether, the formulated material is slower to ignite and slower to burn than the control material which does not contain flame retardant additives. However, when the rubber-modified PMMA compositions which are formulated with the above fire retardant additives do burn, the smoke evolution increases.
A definite need exists in the art of rubber-modified PMMA based molding compositions which have better flame retardancy properties, i.e., slower to ignite and/or slower to burn and which exhibit levels of smoke evolution of less than 300 D.sub.m (Flaming).